**1. Introduction**

In delusional misidentification syndromes (DMSs), the individual everlastingly misidentifies persons, places, objects, or events. Capgras syndrome (CS) is the most common in the umbrella term DMS [1, 2]. Perhaps the best known form of DMS is the *Capgras syndrome*, originally described by Dr. Joseph Capgras and his colleague, J. Reboul-Lachaux, in the early twentieth century [3]. They first encounter this impressive phenomenon when their patient Madame M. insisted that all her friends, family, relatives, and neighbors were being replaced or constantly misperceived as being an imposter [4]. The term *l'illusion des sosies* (the illusion of doubles) was used to describe the case of a woman who strongly believes that various "doubles" had taken the place of people she knew [3]. It is an essential feature of the Capgras syndrome, the denial of identity of known persons and the delusional belief that this person has been substituted by a double [5].

CS is characterized by the delusional denial of identity of a significant other and the belief that they have been replaced by a double. Some patients with CS may deny the identity of the actual spouse and claim that there are two spouses, the actual and the imposter [6]. Therefore there are four conditions in patient with CS: the person is recognized, and the patient affirms the resemblance of the double to the misidentified significant other; no identity is attributed to the double, who has neither name nor existence; the double is an imposter, pretending to be the original they are replacing; the original has disappeared, his/her absence remaining unquestioned [7].

## **2. Features of Capgras syndrome: phenomenology, diagnosis, and epidemiology**

The rareness of CS, as well as its impressive clinical manifestation as a colorful syndrome, has caused most publications to present case descriptions as scientific curiosities [8, 9]. CS has also attracted the attention of novelists in fictional literature. Dostoevsky provided a dramatic description of the phenomenon in his novel, *The Possessed* [6]. Sociocultural factors essentially shape the phenomena and thus mightily influence the establishment of definitions of this disorder [10]. Therefore, it may be necessary to mention. The meaning given to the terms 'change' and 'transformation' of physical identity has been called 'incarnations' or 'possessions' of other bodies in some cultures [10]. Possessions by an evil spirit have early origins within Paganism, Wicca, Haitian voodoo, Buddhism, Hinduism, Judaism, and Christianity [11]. There is a belief in some countries that people can be possessed by Satan and made to act in strange, immoral, and antisocial ways. In the United States, among European-American Catholics, there exists a belief that demons may possess a person. Possessing demons are presumed to cause experiences of proscribed feelings, thoughts, or behaviors in the person. Occasionally, solutions involve exorcism rituals [12].

It is generally being reported as single case studies in the literature. Although an uncommon psychiatric disorder, Capgras delusion has been central to the development of theories of delusions [6]. It is not dealt with particularly in the DSM-5 and may be classified as delusional disorder, suiting either the persecutory or the unspecified type [13]. With no consensual clinical criteria for this syndrome, it is usual to refer to their original description [7]. The basic manifestation was a false belief that real and familiar persons or oneself is replaced by strange, malicious imposters [14]. In fact, CS is a 'hypoidentification' of a person closely related to the patient [6]. CS is more frequent in women than men, with a sex ratio of approximately 2:1, but this result was not found across all studies [7]. Only a few reports have described this syndrome in patients during childhood [15].

The remarkable feature of Capgras delusion is that patients are able to recognize the close relation, the related person's face, but deny his or her identity and often use subtle misperceived differences in behaviour, personality, or physical appearance to distinguish between him or her and the imagined impersonator [16, 17]. Patients with CS find ways to defend their irrational beliefs [4]. Generally, the patients support their conviction in revealing detail. This sign may be a habit or a personality trait; small misperceived differences, for instance, in physical appearance and behaviour, may vary over time [7]. And these are frequently used to distinguish the imposter from the loved one [18]. Surprisingly, patients may show implicit or explicit awareness of their true situation [6]. Some research suggests that a considerable number of patients with CS have some awareness of the bizarre nature of the misidentification delusions and therefore tend not to report them, especially during initial interviews when they are less likely to be confident with the clinician [19].

**121**

*What is Capgras Syndrome? Diagnosis and Treatment Approach*

Common to all DMS is the delusional denial of identity of objects having affective significance for the patient, and it is exceptional for there to be only one imposter, but these objects are limited in number. CS may be associated with other DMSs, and these frequently evolve from one another because of this relation and

It sometimes occurs isolated, hereby justifying its autonomy as a 'delusion' [7]. CS may be accompanied by other delusions and thus may rarely exemplify a 'monothematic' delusion [6]. Erotomanic delusions and delusional jealousy [i.e., Othello jealousy] were identified in 9.1% and 6.4% of patients with CS, respectively [21, 22]. However, delusional misidentification syndromes uncommonly appear

The absence of consensual clinical criteria makes the epidemiological data uncertain [7]. Thus, the prevalence of CS may be underrated. More than half of the patients of the registered cases suffered from mental disorders without any organic association, among which schizophrenia spectrum disorders were diagnosed in 6 of 10 patients with CS [21, 22]. The Capgras delusion has been reported in association with other psychiatric disorders in 60–75% of cases and in organic illnesses in 25–40% of cases [23]. The Capgras delusion has usually been recognized in the contextual relationship of psychiatric disorders and often occurs in conjunction with paranoia, derealization, and depersonalization [6]. The Capgras syndrome may represent a delusional evolution of the phenomena of depersonalization and derealization [24]. Nonspecific, derealization-depersonalization experiences are frequent, especially in psychotic disorders, and are considered a significant core symptom of CS [7]. Studies on the prevalence of this disease or comorbid disease show differences. A study has found that the prevalence of DMS in psychiatric populations was less than 1% [14]. Another study has found that its prevalence in all psychiatric inpatients is 1.3–4.1% [25]. It is around 3% for hospitalized psychotic patients [17]. In a recent prospective study of patients hospitalized for a first psychotic episode, it was found that CS was diagnosed approximately 1 in 10 of patients. The prevalence was maximal among patients presenting schizophreniform psychosis 50%, brief psychosis 34.8%, and unspecified psychosis 23.9%, and the prevalence was moderate for a major depressive episode 15%, schizophrenia 11%, or delusional disorders 11% [14]. The most common psychiatric diagnoses in CS have been paranoid schizophrenia, schizoaffective disorder, and bipolar affective disorder [23]. CS has been linked with multiple pathologies. It has been described in psychiatric as well as organic disorders. In the last few decades, reports have increasingly stressed the aetiologic importance of heterogeneity of conditions that have been found in the patients with misidentification syndromes like the Capgras delusion, including cerebrovascular disease, post-traumatic encephalopathy, temporal lobe epilepsy, postencephalitic Parkinsonism, viral encephalitis, migraine, vitamin B12 deficiency, hepatic encephalopathy, chronic alcoholism, hypothyroidism, pseudohypoparathyroidism, and dementia [23]. Schizophrenia remains the most common co-occurring mental disorder associated with case reports of Capgras delusion [25, 26]. Also, family history of psychosis is reportedly present in half of CS patients [20]. Medications

*DOI: http://dx.doi.org/10.5772/intechopen.91153*

independent of comorbid pathology [23].

and drug toxicity have also been reported to cause CS [27].

Since initial reports of CS involved patients with psychiatric illness, their close relations, and how they interacted with each other, early explanations of the delusion were predominately psychodynamic interpretations. There are several psychodynamic approaches. Consequently, these explanations included suggestions

**3. Explanations for Capgras syndrome**

similarity [7, 20].

*Anxiety Disorders - The New Achievements*

**and epidemiology**

involve exorcism rituals [12].

CS is characterized by the delusional denial of identity of a significant other and the belief that they have been replaced by a double. Some patients with CS may deny the identity of the actual spouse and claim that there are two spouses, the actual and the imposter [6]. Therefore there are four conditions in patient with CS: the person is recognized, and the patient affirms the resemblance of the double to the misidentified significant other; no identity is attributed to the double, who has neither name nor existence; the double is an imposter, pretending to be the original they are replacing; the original has disappeared, his/her absence remaining unquestioned [7].

**2. Features of Capgras syndrome: phenomenology, diagnosis,** 

The rareness of CS, as well as its impressive clinical manifestation as a colorful syndrome, has caused most publications to present case descriptions as scientific curiosities [8, 9]. CS has also attracted the attention of novelists in fictional literature. Dostoevsky provided a dramatic description of the phenomenon in his novel, *The Possessed* [6]. Sociocultural factors essentially shape the phenomena and thus mightily influence the establishment of definitions of this disorder [10]. Therefore, it may be necessary to mention. The meaning given to the terms 'change' and 'transformation' of physical identity has been called 'incarnations' or 'possessions' of other bodies in some cultures [10]. Possessions by an evil spirit have early origins within Paganism, Wicca, Haitian voodoo, Buddhism, Hinduism, Judaism, and Christianity [11]. There is a belief in some countries that people can be possessed by Satan and made to act in strange, immoral, and antisocial ways. In the United States, among European-American Catholics, there exists a belief that demons may possess a person. Possessing demons are presumed to cause experiences of proscribed feelings, thoughts, or behaviors in the person. Occasionally, solutions

It is generally being reported as single case studies in the literature. Although an uncommon psychiatric disorder, Capgras delusion has been central to the development of theories of delusions [6]. It is not dealt with particularly in the DSM-5 and may be classified as delusional disorder, suiting either the persecutory or the unspecified type [13]. With no consensual clinical criteria for this syndrome, it is usual to refer to their original description [7]. The basic manifestation was a false belief that real and familiar persons or oneself is replaced by strange, malicious imposters [14]. In fact, CS is a 'hypoidentification' of a person closely related to the patient [6]. CS is more frequent in women than men, with a sex ratio of approximately 2:1, but this result was not found across all studies [7]. Only a few reports

The remarkable feature of Capgras delusion is that patients are able to recognize the close relation, the related person's face, but deny his or her identity and often use subtle misperceived differences in behaviour, personality, or physical appearance to distinguish between him or her and the imagined impersonator [16, 17]. Patients with CS find ways to defend their irrational beliefs [4]. Generally, the patients support their conviction in revealing detail. This sign may be a habit or a personality trait; small misperceived differences, for instance, in physical appearance and behaviour, may vary over time [7]. And these are frequently used to distinguish the imposter from the loved one [18]. Surprisingly, patients may show implicit or explicit awareness of their true situation [6]. Some research suggests that a considerable number of patients with CS have some awareness of the bizarre nature of the misidentification delusions and therefore tend not to report them, especially during initial interviews when they are less likely to be confident with the clinician [19].

have described this syndrome in patients during childhood [15].

**120**

Common to all DMS is the delusional denial of identity of objects having affective significance for the patient, and it is exceptional for there to be only one imposter, but these objects are limited in number. CS may be associated with other DMSs, and these frequently evolve from one another because of this relation and similarity [7, 20].

It sometimes occurs isolated, hereby justifying its autonomy as a 'delusion' [7]. CS may be accompanied by other delusions and thus may rarely exemplify a 'monothematic' delusion [6]. Erotomanic delusions and delusional jealousy [i.e., Othello jealousy] were identified in 9.1% and 6.4% of patients with CS, respectively [21, 22]. However, delusional misidentification syndromes uncommonly appear independent of comorbid pathology [23].

The absence of consensual clinical criteria makes the epidemiological data uncertain [7]. Thus, the prevalence of CS may be underrated. More than half of the patients of the registered cases suffered from mental disorders without any organic association, among which schizophrenia spectrum disorders were diagnosed in 6 of 10 patients with CS [21, 22]. The Capgras delusion has been reported in association with other psychiatric disorders in 60–75% of cases and in organic illnesses in 25–40% of cases [23]. The Capgras delusion has usually been recognized in the contextual relationship of psychiatric disorders and often occurs in conjunction with paranoia, derealization, and depersonalization [6]. The Capgras syndrome may represent a delusional evolution of the phenomena of depersonalization and derealization [24]. Nonspecific, derealization-depersonalization experiences are frequent, especially in psychotic disorders, and are considered a significant core symptom of CS [7]. Studies on the prevalence of this disease or comorbid disease show differences. A study has found that the prevalence of DMS in psychiatric populations was less than 1% [14]. Another study has found that its prevalence in all psychiatric inpatients is 1.3–4.1% [25]. It is around 3% for hospitalized psychotic patients [17]. In a recent prospective study of patients hospitalized for a first psychotic episode, it was found that CS was diagnosed approximately 1 in 10 of patients. The prevalence was maximal among patients presenting schizophreniform psychosis 50%, brief psychosis 34.8%, and unspecified psychosis 23.9%, and the prevalence was moderate for a major depressive episode 15%, schizophrenia 11%, or delusional disorders 11% [14]. The most common psychiatric diagnoses in CS have been paranoid schizophrenia, schizoaffective disorder, and bipolar affective disorder [23]. CS has been linked with multiple pathologies. It has been described in psychiatric as well as organic disorders. In the last few decades, reports have increasingly stressed the aetiologic importance of heterogeneity of conditions that have been found in the patients with misidentification syndromes like the Capgras delusion, including cerebrovascular disease, post-traumatic encephalopathy, temporal lobe epilepsy, postencephalitic Parkinsonism, viral encephalitis, migraine, vitamin B12 deficiency, hepatic encephalopathy, chronic alcoholism, hypothyroidism, pseudohypoparathyroidism, and dementia [23]. Schizophrenia remains the most common co-occurring mental disorder associated with case reports of Capgras delusion [25, 26]. Also, family history of psychosis is reportedly present in half of CS patients [20]. Medications and drug toxicity have also been reported to cause CS [27].
